A lidar sensor is a light detection and ranging sensor. It is an optical remote sensing module that can measure the distance to a target or objects in a scene, by irradiating the target or scene with light, using pulses (or alternatively a modulated signal) from a laser, and measuring the time it takes photons to travel to said target or landscape and return after reflection to a receiver in the lidar module. The reflected pulses (or modulated signals) are detected, with the time of flight and the intensity of the pulses (or modulated signals) being measures of the distance and the reflectivity of the sensed object, respectively.
Conventional lidar sensors utilize mechanically moving parts for scanning laser beams. In some systems, including certain systems used in automotive applications, such as advanced driver assist systems (ADAS) and autonomous driving systems, it is preferred to use solid state sensors for a variety of potential advantages including but not limited to higher sensor reliability, longer sensor lifetime, smaller sensor size, lower sensor weight, and lower sensor cost.
Radio frequency (RF) delay lines used for the creation of radar phased arrays were used several decades ago for the solid state steering of radar signals. Photonic integrated circuit (PIC) based delay lines combined with detectors and RF antenna arrays were used two decades ago to improve the precision of delays in the solid state steering of radar signals. PICs with microscale and nanoscale devices can be used to produce optical phased arrays (OPAs), comprising tunable optical delay lines and optical antennas, for the solid state steering of laser beams.
Phased arrays in the optical domain that are produced to date are complex, costly and/or have a different purpose than beam forming and beam steering; some combine spatial filters, optical amplifiers and ring lasers (U.S. Pat. No. 7,339,727), some involve a plurality of optical input beams (U.S. Pat. No. 7,406,220), some involve volume diffraction gratings and a plurality of input directions (U.S. Pat. No. 7,428,100), some combine beams of a plurality of wavelengths (U.S. Pat. No. 7,436,588), some have optical phase reference sources and gain elements (U.S. Pat. No. 7,489,870), some have predetermined areas in the field of view and a plurality of beam forming elements (U.S. Pat. No. 7,532,311), and some have multiple frequencies and multiple optical phase reference sources (U.S. Pat. No. 7,555,217).
Two-dimensional beam forming and steering phased arrays in the optical domain that are produced to date have low yields and are costly because they steer in two dimensions with a complex two-dimensional pixel array.